Looking Up: Jupiter, Venus, Moon do a dance

Tuesday

Nov 25, 2008 at 12:01 AMNov 25, 2008 at 3:28 PM

Be certain to look to the skies over the next few nights (from Nov. 29 through Dec. 1). Should the weather cooperate, the view to the southwest during evening twilight should be amazing. Jupiter will be just above Venus, and the crescent moon will be nearby.

Peter Becker

Be certain to look to the skies over the next few nights (from Nov. 29 through Dec. 1). Should the weather cooperate, the view to the southwest during evening twilight should be amazing. Jupiter will be just above Venus, and the crescent moon will be nearby.

Planetary pairings add to the beauty of the sky. If you are able to get a good photograph of the planets and the moon near each other, you are encouraged to send it to me for use in the next column. Please indicate your name and where you were, and any other information you’d like to add. Pictures may be e-mailed to pbecker@wayneindependent.com or mailed to Peter Becker, c/o The Wayne Independent, P.O. Box 122, Honesdale, PA 18431.

Both planets are very bright, though Jupiter is a bit dimmer. On Saturday night, Nov. 29, the planets will appear the closest, with Jupiter only 2.4 degrees above Venus. If you can picture the Big Dipper, the front stars of the “bowl” are about 5 degrees apart.

You will need a good, low view of the southwest. On the 29th, the thin crescent moon will appear very low, as it emerges from the sun’s glare. Binoculars will aid you. Notice how the middle of the crescent always points toward the location of the sun, which by this time is below the horizon.

Each night, the moon at the same time will be seen farther up and to the left, and the crescent will be thicker. On Sunday night, the moon will be closer to the planets, which are still a bit farther to the left and higher. On Monday night, look for the moon to the immediate upper left of the two planets.

In the course of any given year, you are most likely to catch close pairings of the planets either in the western area of the sky after sunset or in the eastern area shortly before sunrise. This is because the orbits of the other planets, as seen from Earth, seem to bunch up when looking near the sun, about which all the planets circle. A close pairing is referred to as a “conjunction.”

If you use a low-power eyepiece -- with a telescope of course -- you could use just an eyepiece, but you won’t see anything; turn it toward Jupiter and Venus. On Saturday night, the planets will almost be in the same low power field of view. Because they are low in the sky, however, you are looking through many more miles of turbulent air, and your view will not likely be sharp. You should be able to see the gibbous phase of Venus, which will be dazzlingly bright in the telescope. Jupiter’s disc will appear somewhat squashed -- somewhat flattened on the top and bottom, an effect of the fast rotation of the planet, which causes the equatorial region to bulge (and you thought it was from eating too many doughnuts).

Jupiter’s apparent width is a little more than twice the view you will have of Venus. Jupiter is an immense planet, about 87,000 miles wide and 11.5 times as large as Venus. Earth, at 7,918 miles across, is only a little larger than Venus, which has a girth of 7,580 miles. One might assume Jupiter will always appear larger than Venus in a telescope, but due to Venus being much closer to us, the second planet from the sun at times looks much wider than Jupiter, the fifth planet.

Jupiter is presently 34 seconds of arc across, which is just over a half of one minute of arc. There are 60 minutes in 1 degree. The full moon appears approximately 30 minutes of arc across (a half degree). Venus presently is only about 16 seconds of arc across, but when closer to us in its orbit, Venus grows to almost a full minute of arc. Wide and sharp-eyed observers without using binoculars have claimed to be able to see the planet at that time as barely more than a point of light. When Venus is this big, it appears in the telescope as a slim crescent, like the crescent moon. Venus exhibits these phases because it orbits between us and the sun, so we see its dark side.

The moon becomes first-quarter on Dec. 6, when the moon looks half-lit. It’s not called “first half” because the “quarter” refers to the moon being one-quarter, or one-fourth its merry way around Earth. Full moon, then, is halfway around, and I’m about dizzy, so until next week. ...

Keep looking up!

Peter W. Becker is managing editor at The Wayne Independent in Honesdale, Pa. He has been an amateur astronomer since the age of 12, in 1969. He may be reached at pbecker@wayneindependent.com.